Scilab function
Last update : September 1996

line_graph - graph with nodes corresponding to edges

### Calling Sequence

  `g1 = line_graph(g)`

### Parameters

- `g`: graph list of the old graph
- `g1`: graph list of the new graph

### Description

`line_graph` returns the graph `g1` with the nodes corresponding to the edges of the graph `g`. `g1` is defined in the following way: - its nodes correspond to the edges of `g` - 2 nodes of the new graph are adjacent if and only if the corresponding edges of the graph `g` are adjacent.

The coordinates of the nodes of `g1` are given by the middle points of the corresponding edges of `g`.

### Examples

    ta=[1 1 2 4 4 5 6 7 2 3 5 1];
    he=[2 6 3 6 7 8 8 8 4 7 3 5];
    g=make_graph('foo',0,8,ta,he);
    g('node_x')=[281  284  360  185  405  182  118  45];
    g('node_y')=[262  179  130  154  368  248  64  309];
    show_graph(g);
    g1=line_graph(g);
    show_graph(g1,'new');

### See Also

`arc_graph`,